SPRITE红外探测器性能的最佳应用

文章介绍了工作波段为8～12.5μm、工作温度为80K,器件尺寸:长度L=700μm、宽度w=62.5μm、厚度d=7μm、读出区面积wl=62.5μm×50μm(名义值)的8条SPRITE红外探测器制造和性能;描述了器件工作电压和探测器性能的关系;讨论了该探测器在热成像系统中最佳使用偏置应为60V/cm,而不是目前的30V/cm;对SPRITE探测器进行了理论分析,指出:在热成像系统中,偏置为60V/cm的SPRITE探测器将获得最佳应用,其性能优于160元背景限线列探测器;还讨论了探测器的热负载和工作电压的关系.     

HgCdTe体晶的组份均匀性分析

利用ＳＰＲＩＴＥ探测器的截止波长研究了布里奇曼、Ｔｅ溶剂和固态再结晶３种方法制备的ＨｇＣｄＴｅ体晶组份的均匀性。实验结果表明：３种方法生长的ＨｇＣｄＴｅ晶片的组份均匀性大致相当。用任意一种材料研制的一个８条ＳＰＲＩＴＥ探测器,其任意２条的截止波长差不大于０．８μｍ的概率大于９８％。     

SPRITE探测器调制传递函数测试方法研究

研究和测量SPRITE探测器调制传递函数(MTF),是为了分析、评价该探测器的空间分辨性能.先前的研究论文己报道了多种测试方法,本文据此进行了分析、研究,提出了基于平面干涉条纹的空间正弦波响应测试方法.该方法能消除光源、测试目标和光学成像系统引入的测量偏差,而且便于多光谱段的SPRITE探测器MTF测试.     

光学投影系统对SPRITE探测器MTF测试的影响

ＳＰＲＩＴＥ探测器是一种三引极ｎ型的ＨｇＣｄＴｅ光电导探测器,具有焦平面上的时间延迟积分（ＴＤＩ）功能,用于串扫和串并扫热成像系统。用建立在线性滤波理论基础上的调制传递函数（ＭＴＦ）评价、测试ＳＰＲＩＴＥ探测器的空间分辨能力,已有不少研究论文报道,但都忽略了测试用光学投影系系统对探测器ＭＴＦ测试的影响。除了光学镜头的传递特性外,光学投影系统中所特有的扫描部件的运动效应也较大程度上影响着探测器ＭＴＦ     

线列探测器实时非均匀校正技术研究

目前线列探测器仍在一些重大工程项目中广泛应用,且多采用两点定标法实现非均匀性的校正.两点定标法需要不断定标以更新校正系数.为了研究能够实现实时校正的方法,主要针对线列探测器的非均匀性特点,对目前几种简单的自适应非均匀校正算法进行分析,并给出了VC6.0++中对MODIS数据的仿真结果.实验表明,恒定统计量算法中参数的选择很难确定,神经网络算法并不适于线列探测器的非均匀校正,重点分析了SPRITE热像仪所采用的归一法,并对其加以改进,使硬件实现更简单、快速.最后,给出了一种采用DSP和CPLD的硬件实现方案,可以完成线列探测器的实时非均匀校正.     

8×2元SPRITE探测器对热成像系统性能改善的模拟分析

研究了采用CCD实现移位延时的nv×ns元SPRITE探测器的性能模型,分析了相对于nv×1元SPRITE探测器对热成像系统性能的改善,模拟计算表明:采用串联技术可满足实际高性能热成像系统的需求.同时,此研究也扩展了热成像系统性能模型的适用范围,对于热成像系统的性能分析、方案论证以及优化设计等都有实际意义.     

The internal magnetic field distribution, and single exponential magnetic resonance free induction decay, in rocks

When fluid saturated porous media are subjected to an applied uniform magnetic field, an internal magnetic field, inside the pore space, is induced due to magnetic susceptibility differences between the pore-filling fluid and the solid matrix. The microscopic distribution of the internal magnetic field, and its gradients, was simulated based on the thin-section pore structure of a sedimentary rock. The simulation results were verified experimentally. We show that the 'decay due to diffusion in internal field' magnetic resonance technique may be applied to measure the pore size distribution in partially saturated porous media. For the first time, we have observed that the internal magnetic field and its gradients in porous rocks have a Lorentzian distribution, with an average gradient value of zero. The Lorentzian distribution of internal magnetic field arises from the large susceptibility contrast and an intrinsic disordered pore structure in these porous media. We confirm that the single exponential magnetic resonance free induction decay commonly observed in fluid saturated porous media arises from a Lorentzian internal field distribution. A linear relationship between the magnetic resonance linewidth, and the product of the susceptibility difference in the porous media and the applied magnetic field, is observed through simulation and experiment.     

Membrane gas diffusion measurements with MRI

Gas transport across polymeric membranes is fundamental to many filtering and separation technologies. To elucidate transport mechanisms, and understand the behaviors of membrane materials, accurate measurement of transport properties is required. We report a new magnetic resonance imaging (MRI) methodology to measure membrane gas phase diffusion coefficients. The MRI challenges of low spin density and short gas phase relaxation times, especially for hydrogen gas, have been successfully overcome with a modified one-dimensional, single-point ramped imaging with T(1) enhancement, measurement. We have measured the diffusion coefficients of both hydrogen gas and sulfur-hexafluoride in a model polymeric membrane of potential interest as a gas separator in metal hydride batteries. The experimental apparatus is a modified one-dimensional diaphragm cell which permits measurement of the diffusion coefficient in experimental times of less than 1 min. The H(2) gas diffusion coefficient in the membrane was 0.54 +/- 0.01 mm(2)/s, while that of sulfur-hexafluoride was 0.14 +/- 0.01 mm(2)/s, at ambient conditions.     

Chemically selective NMR imaging of a 3-component (solid-solid-liquid) sedimenting system

A novel magnetic resonance imaging (MRI) technique which resolves the separate components of the evolving vertical concentration profiles of 3-component non-colloidal suspensions is described. This method exploits the sensitivity of MRI to chemical differences between the three phases to directly image the fluid phase and one of the solid phases, with the third phase obtained by subtraction. 19F spin-echo imaging of a polytetrafluoroethylene (PTFE) oil was interlaced with 1H SPRITE imaging of low-density polyethylene (LDPE) particles. The third phase was comprised of borosilicate glass spheres, which were not visible while imaging the PTFE or LDPE phases. The method is demonstrated by performing measurements on 2-phase materials containing only the floating (LDPE) particles, with the results contrasted to the experimental behaviour of the individual phases in the full 3-phase system. All experiments were performed using nearly monodisperse particles, with initial suspension volume fractions, phi(i), of 0.1.     

Centric scan SPRITE magnetic resonance imaging

Two rapid, pure phase encode, centric scan, Single Point Ramped Imaging with T₁-Enhancement (SPRITE) MRI methods are described. Each retains the benefits of the standard SPRITE method, most notably the ability to image short T₂^* systems, while increasing the sensitivity and generality of the technique. The Spiral-SPRITE method utilizes a modified Archimedean spiral k-space trajectory. The Conical-SPRITE method utilizes a system of spirals mapped to conical surfaces to sample the k-space cube. The sampled k-space points are naturally Cartesian grid points, eliminating the requirement of a re-gridding procedure prior to image reconstruction. The effects of transient state behaviour on image resolution and signal/noise are explored.